1. Field of the Invention
The present invention relates to a production apparatus of a planer type semiconductor device welding an interconnector to a planer type semiconductor element, and a method of fabricating a planer type semiconductor device.
2. Description of the Background Art
An example of a production apparatus of a planer type semiconductor device having an interconnector to lead out an output of a conventional planer type semiconductor element connected by parallel gap welding, and a method of fabricating a planer type semiconductor device will be described with reference to FIGS. 12 and 13. A planer type semiconductor element 105 is placed and fixed on a weld bed 106. An interconnector 103 is disposed on an electrode 104 of planer type semiconductor element 105. Weld electrodes 101 and 102 are abutted against interconnector 103. Load is applied on weld electrodes 101 and 102, and a current is conducted across weld electrodes 101 and 102. Welding is effected by the resistance heat generated here. Welding is repeatedly conducted by moving weld electrodes 101 and 102 corresponding to the width of interconnector 103.
In the above-described conventional production apparatus, aluminum is generally used for the material of weld bed 106 on which planer type semiconductor element 105 is placed. Aluminum is used by virtue of its workability and low cost. It is to be noted that aluminum has an extremely high thermal conductivity. When aluminum is used for weld bed 106, the heat generated for welding will escape through weld bed 106. There was a problem that sufficient welding cannot be achieved, resulting in degradation of the weld strength.
According to a welding method using the conventional production apparatus of a planer type semiconductor device, welding is repeatedly conducted when there are a plurality of welding positions P for one interconnector 103. Therefore, the temperature of weld electrodes 101 and 102 and weld bed 106 of interconnector 103 sequentially rises from the first site of welding to the second site, third site, and on, and is not stable. Also, the escaping manner of heat during welding differs depending upon weld position P. By this difference in temperature, sufficient welding may not be achieved at some parts. There is a problem that weld strength is degraded. Likewise, in the case where the welding operation is carried out continuously for two times or more, the temperature of weld electrodes 101 and 102 and weld bed 106 will sequentially rise from the first welding operation, and is not stable.
In a welding method using a conventional production apparatus of a planer type semiconductor device, a current is conducted across weld electrodes 101 and 102 to generate resistance heat for welding. At this stage, weld electrodes 101 and 102 glow and attain a high temperature to react with oxygen in the air. As a result, weld electrodes 101 and 102 will be oxidized. Nitrogen gas is blown out through a nozzle to weld electrodes 101 and 102 to minimize such oxidation (refer to FIG. 12). However, oxidation cannot be prevented sufficiently by just this blowing measure. As oxidation proceeds, the resistance of weld electrodes 101 and 102 becomes higher to shorten the lifetime. Increasing this lifetime is one issue from the standpoint of cost.
An object of the present invention is to provide a planer type semiconductor device production apparatus that can effect favorable welding, and a method of fabricating a planer type semiconductor device using such a production apparatus.
According to the present invention, a planer type semiconductor device production apparatus electrically connects an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element through parallel gap welding. A weld bed on which is placed the planer type semiconductor element that is to be welded is formed of a material with stainless steel as the main component.
By employing a weld bed with stainless steel as the main component in the planer type semiconductor device production apparatus of the present aspect, the thermal conductivity becomes lower than the thermal conductivity of the generally used aluminum weld bed. Therefore, the heat generated for welding will not escape through the bed. Thus, favorable welding can be conducted.
According to a planer type semiconductor device production apparatus of another aspect of the present invention that electrically connects an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element through parallel gap welding, a weld bed on which is placed a planer semiconductor element to be welded is formed of a material with ceramics as the main component.
By using a weld bed with ceramics as the main component in the planer type semiconductor device production apparatus of the present aspect, the thermal conductivity becomes lower than the thermal conductivity of the generally used aluminum weld bed. Therefore, the heat generated for welding will not escape through the bed. Thus favorable welding can be conducted. Furthermore, the apparatus of the present aspect with a weld bed formed mainly of ceramics is higher in performance than the apparatus with a weld bed formed mainly of stainless steel since ceramics has a lower thermal conductivity than stainless steel.
According to a planer type semiconductor device production apparatus of a further aspect of the present invention that electrically connects an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element through parallel gap welding, a weld bed temperature control mechanism is provided to control the temperature of the weld bed on which is placed a planer type semiconductor element to be welded.
By having the weld bed hold heat in advance through the control of the temperature of the weld bed by the planer type semiconductor device production apparatus of the present aspect, the heat generated for welding will not be depleted by the bed. Thus, favorable welding can be conducted.
Preferably in the planer type semiconductor device production apparatus of the present invention, the area of the plane of the weld bed where the planer type semiconductor element to be welded is placed is set to be not more than the area of the planer type semiconductor element in contact with the plane of the weld bed.
By such a planer type semiconductor device production apparatus, the heat quantity depleted by the weld bed among the heat generated for welding is reduced. Thus, favorable welding can be conducted.
In the planer type semiconductor device production apparatus of the present invention, the thickness of the weld bed may be not more than 3 mm.
By using a weld plate set as thin as possible in structure in such a planer type semiconductor device production apparatus, the heat capacity can be reduced to the best possible degree. Therefore, the heat quantity depleted by the weld bed among the heat generated for welding is reduced. Thus, favorable welding can be conducted.
According to still another aspect of the present invention, a planer type semiconductor device fabrication method electrically connect an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element through parallel gap welding. When there are at least two welding positions in one interconnector in the welding process through parallel gap welding, the power for welding is set for each welding position.
Accordingly, the power at the position where the welding strength was low can be increased whereas the power at the welding position where excessive power was applied can be reduced. Thus, favorable welding can be conducted.
In a planer type semiconductor device fabrication method electrically connecting an interconnector to lead an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element through parallel gap welding of a still further aspect of the present invention, the power for welding can be set in advance for each welding operation when the welding operation is carried out at least two times successively in the welding process through the parallel gap welding.
The power for welding can be set relatively high since the temperature of the welding electrodes and the weld bed is low at the first welding operation. The power for welding can be set lower thereof for the second operation. Appropriate setting is allowed for the third welding operations and et seq. so that stable welding temperature can be achieved. Thus, favorable welding can be conducted.
In a planer type semiconductor device fabrication method electrically connecting an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element according to yet a further aspect of the present invention, welding is conducted with the surrounding of at least a weld electrode set in a gas atmosphere that suppresses oxidation of the weld electrode in the weld process through parallel gap welding.
By setting the surrounding of the weld electrode in a gas atmosphere in the planer type semiconductor device fabrication method, the glow and oxidation of the weld electrode during welding can be suppressed. Thus, the lifetime of the weld electrode can be increased.
In a planer type semiconductor device fabrication method that electrically connects an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of a planer type semiconductor element through parallel gap welding according to yet another aspect of the present invention, welding is conducted with the surrounding of at least a weld electrode in vacuum in the welding process through parallel gap welding.
Accordingly, the glow and oxidation of the weld electrode during welding can be suppressed. Thus, the lifetime of the weld electrode can be increased.
In a planer type semiconductor device fabrication method that electrically connects an interconnector to lead out an output of a planer type semiconductor element with an external output electrode of the planer type semiconductor element through parallel gap welding according to yet a still further aspect of the present invention, a weld bed on which is placed a planer type semiconductor element to be welded is formed of a material with stainless or ceramics as the main component. The temperature of the weld bed with stainless steel or ceramics as the main component is controlled using a weld bed temperature control mechanism. Also, the power for welding is set for at least either each welding operation or each welding position.
According to the planer type semiconductor device fabrication method, the temperature of the weld bed is controlled so that the heat generated for welding will not be depleted through the weld bed. Also, welding can be conducted with an appropriate power for welding corresponding to at least either the welding position or welding operation.
In the planer type semiconductor device production apparatus or planer type semiconductor device fabrication method of the present invention, weld electrodes may be formed of an electrode with tungsten (W) as the main component and an electrode with copper (Cu) as the main component.
By using an electrode with tungsten as the main component and an electrode with copper as the main component for parallel gap welding, the effect of conducting favorable welding can be exhibited more significantly.
In a planer type semiconductor device fabrication method or planer type semiconductor device fabrication method of the present invention, the interconnector may have a comb shape with a slit. Accordingly, the effect of conducting favorable welding can further be exhibited more significantly.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.